The present inventions are related to systems and methods for accessing a storage medium, and more particularly to systems and methods for determining the location of a read/write head assembly in relation to a storage medium.
Writing information to a magnetic storage medium typically includes generating a magnetic field in close proximity to the storage medium to be written. This may be done using a read/write head assembly as are commonly known in the art, and is highly dependent on properly positioning the read/write head assembly in relation to a magnetic storage medium. The distance between the read/write head assembly and the storage medium is commonly referred to as fly-height. Proper control of the fly-height helps to assure that the read back signal exhibits the best possible signal-to-noise ratio, and thereby improves performance.
In a typical implementation, fly-height is determined based on harmonic measurements from data derived from the storage medium. Harmonic single frequency magnitude calculations have typically been performed using a single discrete Fourier transform type integration and calculation. In general, such an approach relies on multiplying the input data stream by two correlation sequences where the correlation sequences are sine and cosine wave samples at a desired frequency to be measured. For very accurate measurements, the aforementioned correlation is performed over a large number of samples. The final magnitude developed over the number of samples is calculated by taking the square root of the sum of squares of the sine and cosine integration results. In such a case where the frequency is the Nyquist frequency, then such a method is dependent on the sampling phase of the measured signal. For example, if a Nyquist pattern is sampled at the zero crossings, then the result of the approach is zero. In contrast, a maximum value results where the Nyquist pattern is sampled at the peaks. As such, the performance of an equalization and timing loop directly impacts the result, thereby limiting the effectiveness of the harmonic measurement.
Hence, for at least the aforementioned reasons, there exists a need in the art for advanced systems and methods for determining fly-height.